STRUCTURE DETERMINATION OF GAMMA'-FE4N AND EPSILON-FE3N

Single crystals of gamma'-Fe4N were prepared by high pressure ammonoly sis. Our earlier published results (H. Jacobs and J. Beck, J. Less-Com mon Met., 134 (1987) 215) differ from those which are now reported, ga mma'-Fe4N crystallizes in the CaTiO3 (perovskite) structure type: X-ra y single-crystal diffractometer data, space group Pm (3) over bar m, Z =1 and a=3.7900(6) Angstrom, R/R(w) (w=1)=0.017/0.023,N(F-0(2))greater than or equal to 3 sigma(F-0(2))=59 and N(var)=6. Powder samples of e psilon-Fe3N were prepared in a technical furnace. The crystal structur e was studied by neutron powder diffraction at 9 K, room temperature a nd 609 K. epsilon-Fe3N crystallizes in a hexagonal structure type: spa ce group P6(3)22, Z=2, a=4.6982(3) Angstrom and c=4.3789(3) Angstrom, N(F-0)=34 and 5 structural parameters refined, R(Profile)=4.43%, R(Bra gg)=4.14% for the measurement at room temperature.